FRANKFURT, Sept 21 (Reuters) - Buyout group Lone Star is considering a stock market flotation of German building materials maker Xella which it bought in 2016 for 2.2 billion euros ($2.6 billion), three people close to the matter said.

The investor could opt for a second-quarter listing in Frankfurt, the people said, adding that it recently interviewed investment banks and asked for their ideas to develop the company.

However, so far no formal pitching process for roles in a potential initial public offering has taken place and no decision on any deal has been taken, they added.